268 Mary A. Bowers. 



Duesberg describes the epithelium of the coil at a time before the 

 appearance of the hind legs, as composed of principal cells and, be- 

 tween their proximal ends, scattered basal cells. Later, as the hind 

 legs appear, other basal elements are noticed, which clearly cor- 

 resjjond to Renter's round cell. Vacuoles and granules appear in the 

 protoplasm, neighboring cells become confluent and form a single 

 cell, the brown masses become more numerous, the nuclei go through 

 chromatolysis, and the final stage in this process is the typical "round 

 cell." These cells present none of the characteristics of active ab- 

 sorbing cells, on the contrary they, show marked degenerative phe- 

 nomena. They are cast off as described by Reuter. 



Duesberg figures the definitive epithelium as forming from the 

 basal cells of the larval epithelium, which are at first not distinguished 

 by any peculiar structure, but later show the characteristics of 

 Renter's "giant cells." He has not seen in any of his preparations the 

 formation of round or of giant cells by amitotic division of the prin- 

 cipal cells. 



My conclusions, which agree in the main points with those of Dues- 

 berg, were formed independently before the reading of his paper. 



II. Description. The histological differentiation of the small 

 intestine of Bufo, i. e., the degeneration and regeneration of the 

 epithelium, takes place progressively from the anterior to the posterior 

 end. Therefore, for clearness of comparison in successive stages, one 

 particular region has been selected for description, the duodenum 

 near the entrance of the bile duct, and all figures except 16 and 44 

 are from this region of the intestine. 



At the time of hatching the stomodeum and proctodeum are already 

 formed and the rest of the alimentary canal is a mass of yolk, through 

 the dorsal portion of which runs an irregular lumen. Anteriorly, ex- 

 tending back to the level of the pronephros, the lumen is definite, and 

 in the dorsal and lateral walls may be distinguished scattered nuclei 

 and very faint irregular cell walls. 



Fig. 22, five days after hatching, shows the earliest differentia- 

 tion of the duodenal epithelium into a definite layer of columnar cells. 

 The cell walls are very faint, the ciliated border is not formed, the 

 cells are solidly packed with yolk spherules and often contain two 

 nuclei. 



